Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.96	10.585%	$112.7525	$112.75	$112.75	$112.80
Purchase #2	$72.59	13.693%	$82.5297	$82.53	$82.55	$82.50
Purchase #3	$115.70	4.469%	$120.8706	$120.87	$120.85	$120.90
Purchase #4	$38.99	6.536%	$41.5384	$41.54	$41.55	$41.50
Purchase #5	$227.86	8.425%	$247.0572	$247.06	$247.05	$247.10
Purchase #6	$167.90	3.364%	$173.5482	$173.55	$173.55	$173.50
Purchase #7	$71.38	6.638%	$76.1182	$76.12	$76.10	$76.10
7 purchase totals =	$796.38		$854.4148	$854.42	$854.40	$854.40